The term "pagan" is a catch-all term used to describe anyone who doesn't follow the Builders' religion--in particular those who live in the wilds outside the city. It is considered synonymous with "barbarian". There are many different pagan tribes, each with their own traditions and appearance. They don't refer to themselves as "pagans", nor do they necessarily cooperate with each other. They should not be thought of as a single "faction". The only thing they all have in common is a connection to the natural world and devotion to the old gods.
Pagans (also referred to as barbarians or savages) generally live in small tribes and villages outside the city. Some pagan tribes are fairly pleasant, trading peacefully with nearby villages, while others (generally further from the city) are highly aggressive, warring with neighbouring tribes and raiding settlements. Some tribes living deep in the wilds are said to be truly savage, wearing the skulls of animals and eating the flesh of men.
Pagans generally have a close relationship with nature and magical forces. They worship animal and nature spirits to varying degrees. Some simply venerate them; other tribes have members that can actually take on animal form. Most tribes have one or more shamans or druids who are wise in the ways of natural magic--able to conduct powerful rituals to keep their tribes safe or bring ruin on their enemies.
The culture and customs of pagan tribes can be thought of as a mixture of "tribal" societies from our own history, including celtic, germanic, gallic and basque tribes. They are frequently covered by bizzarre tattoos, piercings, and wear the furs and bones of animals. Anyone with tattoos or bizarre hairstyles is often assumed to be a pagan even if they are not.
Pagans Within the City
There are some pagans who have taken to living inside the walls of Bridgeport (The City). They originally came from tribes close to the city to begin with, and wound up taking jobs inside the walls. Although they are forbidden to own land, some still move to the city looking for work or other opportunities.
Sometimes these "urban pagans" join the Church and gradually assimilate into cosmopolitan society. They cut their hair, go to mass, and eventually become indistinguishable from other citizens of Bridgeport. In other cases, they cling to their old beliefs and continue to practice their religion and culture--a decision that often makes them a target of bigots and religious zealots.
Urban pagans live in their own district in the city, for the most part. As they are forbidden from becoming landowners, they rent from sympathetic or opportunistic landlords.
Pagan beliefs generally involve magic and nature-worship, practices which make them feared and mistrusted by the rest of society. They live in fear of the Builders, who can usually arrest them for heresy without comment. Few will come to the aid of a pagan. When fires, disease or other problems arise in the city they are often the first to be blamed.
Pagans are not "eco-terrorists". They generally have no particular objection to technology or civilization, though they may feel uncomfortable around it (like any rural person in a big city for the first time).
Pagans do not see themselves as "at war" with the Builders or their religion (though they certainly fear them). Since pagans are pantheistic, they have no problem with the existence of many gods.
Pagans are not mages and have no special friendship with those who are--while pagans are more comfortable with natural magic than most, academic sorcery is totally foreign to them.
Pagans do not all get along, and do not all worship the same gods.